Hall of Infinite Doors

The hallway seems to abruptly stop. You notice a giant hole in the end of the hallway, almost like an extension of the hallway was carved out of the wall when someone reached this end before you. There is a track going into this dark cave-like tunnel and a mining cart on it complete with one of those helmets with a light on top of it and a pickax. Figuring that you have come this far, you hop on into the cart which automatically starts moving into the dark tunnel...